There is a demand for detection of a target in various fields such as a clinical treatment field, a food field, and an environment field. For the detection of a target, commonly, a method using an antibody that specifically binds to the target is widely used as a method that utilizing an interaction with the target. In these years, a method using a nucleic acid molecule (so called aptamer) that is specific to the target instead of the antibody is newly developed.
As the method using the aptamer, for example, a sensor in which an aptamer and DNAzyme are linked is reported. DNAzyme is a DNA molecule which activates the catalytic activity of a redox reaction similar to peroxidase or the like when it forms a G-quartet. According to such a sensor, it is possible to indirectly detect a target by binding a target to the aptamer and measuring the catalytic activity of the DNAzyme in a sensor in which the target is bound to the aptamer (Non-Patent Document 1).
It is also reported that G-quartet-formed DNAzyme generates fluorescence when it forms a complex with porphyrin (Non-Patent Documents 2 and 3). Hence, newly reported is a method of detecting a target by not measuring the catalytic activity of a redox reaction of DNAzyme but measuring fluorescence generated by the formation of complex in a sensor in which an aptamer and DNAzyme are linked. However, provision of a fluorescence sensor having a novel structure more suitable in practical use is desired.